Device and method of handling hybrid automatic repeat request timing

ABSTRACT

A base station comprised in a network for handling a HARQ timing for a communication device comprises a storage device and a processing circuit coupled to the storage device. The storage device stores instructions, and the processing circuit is configured to execute the instructions of transmitting a first downlink (DL) control information (DCI) for communicating with the communication device according to a first HARQ minimum timing; and transmitting a second DCI for communicating with the communication device according to a second HARQ minimum timing.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of U.S. application Ser.No. 15/674,507, filed on Aug. 10, 2017, which claims the benefit of U.S.Provisional Application No. 62/373,947, filed on Aug. 11, 2016.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to a communication device and a methodused in a wireless communication system, and more particularly, to acommunication device and a method of handling a Hybrid Automatic RepeatRequest (HARQ) timing in a wireless communication system.

2. Description of the Prior Art

An evolution of a long-term evolution (LTE) system is continued toprovide a high data rate and a low latency. In the LTE system, a radioaccess network known as an evolved universal terrestrial radio accessnetwork (E-UTRAN) includes at least one evolved Node-B (eNB) forcommunicating with at least one user equipment (UE), and forcommunicating with a core network including a mobility management entity(MME), a serving gateway (S-GW), etc., for Non-Access Stratum (NAS)control.

SUMMARY OF THE INVENTION

The present invention therefore provides a communication device andmethod for handling a Hybrid Automatic Repeat Request (HARQ) timing in awireless communication system to solve the abovementioned problem.

A base station (BS) comprised in a network for handling a HARQ timingfor a communication device comprises a storage device and a processingcircuit coupled to the storage device. The storage device storesinstructions, and the processing circuit is configured to execute theinstructions of transmitting a first downlink (DL) control information(DCI) for communicating with the communication device according to afirst HARQ minimum timing; and transmitting a second DCI forcommunicating with the communication device according to a second HARQminimum timing.

These and other objectives of the present invention will no doubt becomeobvious to those of ordinary skill in the art after reading thefollowing detailed description of the preferred embodiment that isillustrated in the various figures and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a wireless communication systemaccording to an example of the present invention.

FIG. 2 is a schematic diagram of a communication device according to anexample of the present invention.

FIG. 3 is a flowchart of a process according to an example of thepresent invention.

FIG. 4 is a flowchart of a process according to an example of thepresent invention.

FIG. 5 is a flowchart of a process according to an example of thepresent invention.

FIG. 6 is a flowchart of a process according to an example of thepresent invention.

DETAILED DESCRIPTION

FIG. 1 is a schematic diagram of a wireless communication system 10according to an example of the present invention. The wirelesscommunication system 10 is briefly composed of a network and a pluralityof communication devices. In FIG. 1, the network and the communicationdevices are simply utilized for illustrating the structure of thewireless communication system 10. Practically, the network may be auniversal terrestrial radio access network (UTRAN) including at leastone Node-B (NB) and/or a Radio Network Controller (RNC) in a universalmobile telecommunications system (UMTS). In one example, the network mayinclude an evolved universal terrestrial radio access network (E-UTRAN)comprising at least one evolved NB (eNB). In one example, the networkmay include a fifth generation (5G) network including at least one 5Gbase station (BS) (e.g. gNB) which employs orthogonal frequency-divisionmultiplexing (OFDM) and/or non-OFDM, wide bandwidth (e.g., 100 MHz) andtransmission time interval smaller than 1 millisecond (ms) (e.g., 100 or200 microseconds), to communication with the communication devices. Ingeneral, a BS may also be used to refer to the eNB or the 5G BS.

A communication device may be a user equipment (UE), a machine typecommunication (MTC) device, a mobile phone, a laptop, a tablet computer,an electronic book, a portable computer system, a vehicle, or anaircraft. In addition, the network and the communication device can beseen as a transmitter or a receiver according to direction (i.e.,transmission direction), e.g., for an uplink (UL), the communicationdevice is the transmitter and the network is the receiver, and for adownlink (DL), the network is the transmitter and the communicationdevice is the receiver.

FIG. 2 is a schematic diagram of a communication device 20 according toan example of the present invention. The communication device 20 may bea communication device or the network shown in FIG. 1, but is notlimited herein. The communication device 20 may include a processingcircuit 200 such as a microprocessor or Application Specific IntegratedCircuit (ASIC), a storage device 210 and a communication interfacingdevice 220. The storage device 210 may be any data storage device thatmay store a program code 214, accessed and executed by the processingcircuit 200. Examples of the storage device 210 include but are notlimited to a subscriber identity module (SIM), read-only memory (ROM),flash memory, random-access memory (RAM), hard disk, optical datastorage device, non-volatile storage device, non-transitorycomputer-readable medium (e.g., tangible media), etc. The communicationinterfacing device 220 includes a transceiver transmitting and receivingsignals (e.g., data, signals, messages and/or packets) according toprocessing results of the processing circuit 200.

In the following embodiments, a UE is used to represent a communicationdevice in FIG. 1, to simplify the illustration of the embodiments.

FIG. 3 is a flowchart of a process 30 according to an example of thepresent invention. The process 30 is utilized in a UE, to handling aHybrid Automatic Repeat Request (HARQ) timing and includes the followingsteps:

Step 300: Start.

Step 302: Communicate with a network according to a first HARQ minimumtiming.

Step 304: Transmit a first message comprising an indication of supportof a second HARQ minimum timing to the network according to the firstHARQ minimum timing, wherein the first HARQ minimum timing is greaterthan the second HARQ minimum timing.

Step 306: Receive a second message configuring the second HARQ minimumtiming from the network according to the first HARQ minimum timing.

Step 308: Communicate with the network according to the second HARQminimum timing in response to the second message.

Step 310: End.

According to the process 30, the UE and the network synchronize witheach other according to the reduced HARQ minimum timing (e.g., thesecond HARQ minimum timing).

Realization of the process 30 is not limited to the above description.The following examples may be applied to the process 30.

In one example, the UE establishes a radio resource control (RRC)connection with the network, when communicating with the networkaccording to the first HARQ minimum timing. Then, the UE transmits thefirst message via the RRC connection to the network.

In one example, the indication of the support of the second HARQ minimumtiming is applied for a plurality of component carriers (CCs) in acarrier aggregation (CA) or a dual connectivity (DC). In one example,the indication of the support of the second HARQ minimum timing isapplied for UL CCs or DL CCs in the CA or the DC. In one example, theindication of the support of the second HARQ minimum timing is specificto a CC. In one example, the indication of the support of the secondHARQ minimum timing is specific to a UL, a DL or both the UL and the DL.

In one example, the first HARQ minimum timing may be a first intervalbetween a first transmission time interval (TTI) (e.g., n-th TTI) inwhich the UE receives a first UL grant from the network and a second TTI(e.g., (n+k)-th TTI) in which the UE transmits first UL data accordingto the first UL grant to the network. The second HARQ minimum timing maybe a second interval between a third TTI (e.g., m-th TTI) in which theUE receives a second UL grant from the network and a fourth TTI (e.g.,(m+k′)-th TTI) in which the UE transmits second UL data according to thesecond UL grant to the network. For example, k (e.g., k=4) is greaterthan k′ (e.g., k′=2 or 3). In one example, the UE may receive the firstUL grant in a first DL control information (DCI) with a first cyclicredundancy check (CRC) scrambled with a Cell Radio Network TemporaryIdentifier (C-RNTI) of the UE on a first physical DL control channel(PDCCH) or a first enhanced PDCCH (EPDCCH) (hereafter, a PDCCH refers aPDCCH or an EPDCCH). The UE may receive the second UL grant in a secondDCI with a second CRC scrambled with the C-RNTI of the UE on a secondPDCCH. In one example, formats of the first DCI and the second DCI arethe same or different.

In one example, the first HARQ minimum timing may be a first intervalbetween a first TTI (e.g., a-th TTI) in which the UE transmits first ULdata according to a first HARQ process and a first UL grant to thenetwork and a second TTI (e.g., (a+j)-th TTI) in which the UE receives afirst HARQ feedback indicating whether the first UL data is received ornot or in which the UE receives a second UL grant from the network. Thesecond HARQ minimum timing may be a second interval between a third TTI(e.g., b-th TTI) in which the UE transmits second UL data according to asecond HARQ process and a third UL grant to the network and a fourth TTI(e.g., (b+j′)-th TTI) in which the UE receives a second HARQ feedbackindicating whether the second UL data is received or not or in which theUE receives a fourth UL grant from the network. For example, j (e.g.,j=4) is greater than j′ (e.g., j′=2 or 3). In one example, the UE mayreceive the first UL grant in a first DCI with a first CRC scrambledwith a first C-RNTI of the UE on a first PDCCH. The UE may receive thesecond UL grant in a second DCI with a second CRC scrambled with thefirst C-RNTI of the UE on a second PDCCH, wherein formats of the firstDCI and the second DCI are the same. The UE may receive the first HARQfeedback on a physical hybrid-ARQ indicator channel (PHICH). The UE mayreceive the third UL grant in a third DCI with a third CRC scrambledwith a second C-RNTI of the UE on a third PDCCH. The UE may receive thefourth UL grant in a fourth DCI with a fourth CRC scrambled with thesecond C-RNTI of the UE on a fourth PDCCH. In one example, the firstC-RNTI and the second C-RNTI are the same, and formats of the third DCIand the fourth DCI are the same but different form the formats of thefirst DCI and the second DCI. In another example, the first C-RNTI andthe second C-RNTI are different, and formats of the third DCI and thefourth DCI are the same as the formats of the first DCI and the secondDCI.

In one example, the first HARQ minimum timing may be a first intervalbetween a first TTI (e.g., c-th TTI) in which the UE intends to receivefirst DL data according to a first DL assignment from the network and asecond TTI (e.g., (c+i)-th TTI) in which the UE transmits a first HARQfeedback indicating whether the first DL data is received or not to thenetwork. The second HARQ minimum timing may be a second interval betweena third TTI (e.g., d-th TTI) in which the UE intends to receive secondDL data according to a second DL assignment from the network and afourth TTI (e.g., (d+i′)-th TTI) in which the UE transmits a second HARQfeedback indicating whether the second DL data is received or not to thenetwork. For example, i (e.g., i=4) is greater than i′ (e.g., i′=2 or3). In one example, the UE may receive the first DL assignment in afirst DCI with a first CRC scrambled with a first C-RNTI of the UE on afirst PDCCH. The UE may receive the second DL assignment in a second DCIwith a second CRC scrambled with a second C-RNTI of the UE on a secondPDCCH. The first C-RNTI and the second C-RNTI are the same or different.Formats of the first DCI and the second DCI are the same or different.In one example, the first C-RNTI and the second C-RNTI are the same, andthe formats of the first DCI and the second DCI are different. Inanother example, the first C-RNTI and the second C-RNTI are different,and the formats of the first DCI and the second DCI are the same.

In one example, the first HARQ minimum timing may be a first intervalbetween a first TTI (e.g., e-th TTI) in which the UE transmits a firstHARQ feedback indicating whether first DL data is received or not to thenetwork and a second TTI (e.g., (e+q)-th TTI) in which the UE receives afirst DL assignment from the network. The second HARQ minimum timing maybe a second interval between a third TTI (e.g., f-th TTI) in which theUE transmits a second HARQ feedback indicating whether second DL data isreceived or not to the network and a fourth TTI (e.g., (f+q′)-th TTI) inwhich the UE receives a second DL assignment from the network. Forexample, q (e.g., q=4) is greater than q′ (e.g., q′=2 or 3). In oneexample, the UE may receive the first DL assignment in a first DCI witha first CRC scrambled with a first C-RNTI of the UE on a first PDCCH.The UE may receive the second DL assignment in a second DCI with asecond CRC scrambled with a second C-RNTI of the UE on a second PDCCH.The first C-RNTI and the second C-RNTI are the same or different.Formats of the first DCI and the second DCI are the same or different.In one example, the first C-RNTI and the second C-RNTI are the same, andthe formats of the first DCI and the second DCI are different. Inanother example, the first C-RNTI and the second C-RNTI are different,and the formats of the first DCI and the second DCI are the same.

In one example, k, j, i and q may be a same value or different values.

In one example, the UE may not communicate with the network according tothe first HARQ minimum timing, i.e., the UE may not use the first HARQminimum timing anymore, when the UE is configured to communicate withthe network according to the second HARQ minimum timing.

In one example, the UE may communicate with the network according to atleast one of the first HARQ minimum timing and the second HARQ minimumtiming, when the UE is configured to communicate with the networkaccording to the second HARQ minimum timing. For example, when the UE isconfigured to communicate with the network according to the second HARQminimum timing, the UE uses the first HARQ minimum timing or the secondHARQ minimum timing according to a DCI or a C-RNTI. The DCI and theC-RNTI can be referred to the previous description, and are not narratedherein. The UE may monitor a PDCCH with the DCI indicating the secondHARQ minimum timing or may monitor a PDCCH with the C-RNTI indicatingthe second HARQ minimum timing, when the UE is configured to communicatewith the network according to the second HARQ minimum timing.

In one example, the UE may communicate with the network according to thefirst HARQ minimum timing on a first CC. The UE may communicate with thenetwork according to the second HARQ minimum timing on a second CC.

In one example, the UE may perform a random access (RA) proceduretriggered by one of a UL transmission (e.g., transmission of bufferstatus report or scheduling request), a PDCCH order which is receivedfrom the network and a handover command, when the UE is configured tocommunicate with the network according to the second HARQ minimumtiming. In one example, the UE transmits a RA preamble of the RAprocedure to the network, and receives a RA response from the network ina RA response window. For example, the UE transmits the RA preamble tothe network. The UE receives a first RA response in x-th TTI from thenetwork in response to the RA preamble, wherein the first RA responseincludes a first UL grant (e.g., the random access response grant). TheUE transmits first UL data in (x+y)-th TTI, wherein y is greater than orequals to 6, if a UL delay field in the first UL grant is set to 0,where the (x+y)-th TTI is a first available UL TTI for a physical ULshared channel (PUSCH) transmission. For a FDD serving cell of thenetwork, y equals to 6. For a time-division duplexing (TDD) serving cellof the network, the first available UL TTI for transmitting the first ULdata is determined based on a UL/DL configuration (e.g., the parametersubframeAssignment). The UE postpones the transmission of the first ULdata to the next available UL TTI after the (x+y)-th TTI, if the ULdelay field is set to 1. After the UE transmits the first UL data in the(x+y)-th TTI or the next available UL TTI after the (x+y)-th TTI, the UEreceives a first HARQ feedback or a DCI (indicating a retransmission ofthe first UL data) on a PDCCH according to the first HARQ minimum timing(e.g., in (x+y+4)-th TTI).

In one example, the network (e.g., always) transmits the DCI in thefirst HARQ minimum timing, wherein the DCI indicates a retransmission ofUL data which was transmitted by a UE according to a UL grant in a RAresponse, no matter the UE supports or is configured the second HARQminimum timing.

In one example, the first message may be a Medium Access Control (MAC)control element or a RRC message (e.g., UECapabilityInformation). Thesecond message may be a MAC control element or a RRC message (e.g.,RRCConnectionReconfiguration). In one example, the support of the secondHARQ minimum timing is included in a UE-EUTRA-Capability informationelement.

FIG. 4 is a flowchart of a process 40 according to an example of thepresent invention. The process 40 is utilized in a UE, to handle a HARQtiming and includes the following steps:

Step 400: Start.

Step 402: Communicate with a network according to a first HARQ minimumtiming and a first DCI received from the network.

Step 404: Communicate with the network according to a second HARQminimum timing and a second DCI received from the network.

Step 406: End.

In one example, the first DCI is configured with a first CRC scrambledby a C-RNTI of the UE, and the second DCI is configured with a secondCRC scrambled by the C-RNTI of the UE. The formats of the first DCI andthe second DCI are same or different.

Realization of the process 40 is not limited to the above description.The following examples may be applied to the process 40.

In one example, the UE may communicate (e.g., transmit or receive) withthe network on a first CC according to the first HARQ minimum timing, afirst HARQ process and the first DCI (e.g., the first DCI includes afirst UL grant or a first DL assignment). The UE may communicate (e.g.,transmit or receive) with the network on the first CC or a second CCaccording to the second HARQ minimum timing, a second HARQ process andthe second DCI (e.g., the second DCI includes a second UL grant or asecond DL assignment). The first DCI and the second DCI can be referredto the previous description related to the process 30, and are notnarrated herein.

In one example, the network transmits the second DCI on the first CC orthe second CC to the UE, after the network receives a message comprisingan indication of support of the second HARQ minimum timing. In oneexample, the network transmits the first DCI on the first CC to the UE,after the network receives a message comprising an indication of supportof the second HARQ minimum timing, which can be referred to the previousdescription and is not narrated herein.

FIG. 5 is a flowchart of a process 50 according to an example of thepresent invention. The process 50 is utilized in a BS included in anetwork, to handle a HARQ timing for a UE and includes the followingsteps:

Step 500: Start.

Step 502: Communicate with the UE according to a first HARQ minimumtiming.

Step 504: Receive a first message comprising an indication of support ofa second HARQ minimum timing from the UE according to the first HARQminimum timing, wherein the first HARQ minimum timing is greater thanthe second HARQ minimum timing.

Step 506: Transmit a second message configuring the second HARQ minimumtiming to the UE according to the first HARQ transmission timing inresponse to the first message.

Step 508: Communicate with the UE according to the second HARQtransmission timing, when configuring the second HARQ transmissiontiming to the UE.

Step 510: End.

According to the process 50, the UE and the network synchronize witheach other according to the reduced HARQ minimum timing (e.g., thesecond HARQ minimum timing).

Realization of the process 50 is not limited to the above description.The examples for the process 50 can be referred to the previousdescription related to the process 30, and are not narrated herein.

FIG. 6 is a flowchart of a process 60 according to an example of thepresent invention. The process 60 is utilized in a BS included in anetwork, to handle a HARQ timing for a UE and includes the followingsteps:

Step 600: Start.

Step 602: Transmit a first DCI for communicating with the UE accordingto a first HARQ minimum timing.

Step 604: Transmit a second DCI for communicating with the UE accordingto a second HARQ minimum timing.

Step 606: End.

The following examples may be applied to the processes 30-60.

In one example, the first HARQ minimum timing is longer than the secondHARQ minim timing.

In one example, the network may transmit the first DCI and the secondDCI, after receiving a message comprising an indication of support ofthe second HARQ minimum timing. The network may transmit a first HARQfeedback corresponding to a first PUSCH transmission received from theUE according to the first HARQ minimum timing and a second HARQ feedbackcorresponding to a second PUSCH transmission received from the UEaccording to the second HARQ minimum timing, when the network knows thatthe UE supports the second HARQ minimum timing or before or after thenetwork configures the second HARQ minimum timing. The UE may transmit aPUSCH transmission according to a UL grant included in a RA response orin the first DCI according to the first HARQ minimum timing.

In one example, the UE starts a first HARQ round-trip time (RTT) timerfor a first HARQ process, wherein the first HARQ process is used forcommunicating with the network according to the first HARQ minimumtiming. The UE starts a second HARQ RTT timer for a second HARQ process,wherein the second HARQ process is used for communicating with thenetwork according to the second HARQ minimum timing, wherein a firstlength (e.g., 8 TTIs) of the first HARQ RTT timer is longer than asecond length (e.g., 6 or 4 TTIs) of the second HARQ RTT timer. In oneexample, the first HARQ process and the second HARQ process are DL HARQprocesses, and the first HARQ RTT timer and the second HARQ RTT timerare DL HARQ RTT timers. In one example, the first HARQ process and thesecond HARQ process are UL HARQ processes, and the first HARQ RTT timerand the second HARQ RTT timer are UL HARQ RTT timers.

In one example, the network starts a first HARQ RTT timer for a firstHARQ process, wherein the first HARQ process is used for communicatingwith the UE according to the first HARQ minimum timing. The networkstarts a second HARQ RTT timer for a second HARQ process, wherein thesecond HARQ process is used for communicating with the UE according tothe second HARQ minimum timing, wherein a first length (e.g., 8 TTIs) ofthe first HARQ RTT timer is longer than a second length (e.g., 6 or 4TTIs) of the second HARQ RTT timer. In one example, the first HARQprocess and the second HARQ process are DL HARQ processes, and the firstHARQ RTT timer and the second HARQ RTT timer are DL HARQ RTT timers. Inone example, the first HARQ process and the second HARQ process are ULHARQ processes, and the first HARQ RTT timer and the second HARQ RTTtimer are UL HARQ RTT timers.

Each UL data may be transmitted by the UE in a HARQ transmission or aPUSCH transmission in a TTI, and each DL data may be transmitted by theBS in a HARQ transmission or a physical DL shared channel (PDSCH)transmission in a TTI. The HARQ feedback may be a HARQ acknowledgement(ACK) or a negative acknowledgement (NACK). The TTI may be 1 ms or 0.5ms.

In one example, a field in the DCI above may indicate that the firstHARQ minimum timing or the second HARQ minimum timing is used.

Furthermore, the examples in the processes 30-50 may be applied to theprocess 60, and are not narrated herein.

Those skilled in the art should readily make combinations, modificationsand/or alterations on the abovementioned description and examples. Theabovementioned description, steps and/or processes including suggestedsteps can be realized by means that could be hardware, software,firmware (known as a combination of a hardware device and computerinstructions and data that reside as read-only software on the hardwaredevice), an electronic system, or combination thereof. An example of themeans may be the communication device 20. Any of the above mentionedprocesses may be compiled into the program code 214.

To sum up, the present invention provides a communication device and amethod for handling a HARQ timing for a network including at least oneBS. The UE transmits a message to notify the network which reduced HARQminimum timing is supported. Thus, the problem how the UE and thenetwork synchronize with each other according to the reduced HARQminimum timing is solved.

Those skilled in the art will readily observe that numerousmodifications and alterations of the device and method may be made whileretaining the teachings of the invention. Accordingly, the abovedisclosure should be construed as limited only by the metes and boundsof the appended claims.

What is claimed is:
 1. A base station (BS) comprised in a network forhandling a Hybrid Automatic Repeat Request (HARQ) timing for acommunication device, comprising: a storage device; and a processingcircuit, coupled to the storage device, wherein the storage devicestores instructions, and the processing circuit is configured to executethe instructions of: transmitting a first downlink (DL) controlinformation (DCI) for communicating with the communication deviceaccording to a first HARQ minimum timing; transmitting a second DCI forcommunicating with the communication device according to a second HARQminimum timing; and transmitting a first HARQ feedback corresponding toa first physical uplink (UL) shared channel (PUSCH) transmissionreceived from the communication device according to the first HARQminimum timing and a second HARQ feedback corresponding to a secondPUSCH transmission received from the communication device according tothe second HARQ minimum timing, when the network knows that thecommunication device supports the second HARQ minimum timing or afterthe network configures the second HARQ minimum timing.
 2. The BS ofclaim 1, wherein the storage device further stores the instructions of:transmitting the first DCI and the second DCI, after receiving a messagecomprising an indication of support of the second HARQ minimum timing.3. The BS of claim 1, wherein the storage device further stores theinstructions of: starting a first HARQ round-trip time (RTT) timer for afirst HARQ process, wherein the first HARQ process is used forcommunicating with the communication device according to the first HARQminimum timing; and starting a second HARQ RTT timer for a second HARQprocess, wherein the second HARQ process is used for communicating withthe communication device according to the second HARQ minimum timing,wherein a first length of the first HARQ RTT timer is longer than asecond length of the second HARQ RTT timer.
 4. A method for handling aHybrid Automatic Repeat Request (HARQ) timing for a communication deviceof a base station (BS) comprised in a network, comprising: transmittinga first downlink (DL) control information (DCI) for communicating withthe communication device according to a first HARQ minimum timing;transmitting a second DCI for communicating with the communicationdevice according to a second HARQ minimum timing; and transmitting afirst HARQ feedback corresponding to a first physical uplink (UL) sharedchannel (PUSCH) transmission received from the communication deviceaccording to the first HARQ minimum timing and a second HARQ feedbackcorresponding to a second PUSCH transmission received from thecommunication device according to the second HARQ minimum timing, whenthe network knows that the communication device supports the second HARQminimum timing or after the network configures the second HARQ minimumtiming.
 5. The method of claim 4, further comprising: transmitting thefirst DCI and the second DCI, after receiving a message comprising anindication of support of the second HARQ minimum timing.
 6. The methodof claim 4, further comprising: starting a first HARQ round-trip time(RTT) timer for a first HARQ process, wherein the first HARQ process isused for communicating with the communication device according to thefirst HARQ minimum timing; and starting a second HARQ RTT timer for asecond HARQ process, wherein the second HARQ process is used forcommunicating with the communication device according to the second HARQminimum timing, wherein a first length of the first HARQ RTT timer islonger than a second length of the second HARQ RTT timer.